In tennis, it has become recognized that the tennis racket shall be gripped in different positions for different types of strokes. Basically the strokes may be divided into forehand and backhand, service, volley and overhead strokes. In teaching tennis to a beginner, it is necessary to instruct the student how to hold the racket for a forehand stroke and how to hold the racket for a backhand stroke with modifications for the other types of strokes as well. While it is possible to provide this instruction, it is quite difficult for the student to carry out the instructions during play. It is not possible during a game of tennis to look at the racket and the position of the hand thereon because the player must at all times keep his eye on the tennis ball in order that he will be in the proper position to hit the ball returned by his opponent. Thus, it is necessary for a player to automatically switch his grip upon the racket during play.
The accepted swing of a tennis racket is a motion wherein the momentum of the head of the tennis racket is used to propel the tennis ball. Instructors in the art of playing tennis go to great lengths to impart to their students the kinesthetic or muscular sense which must be developed in using the racket as a centrifugal implement to impact a tennis ball. Unfortunately, this kinesthetic or muscular sense is personal to the student. In many cases, verbal stimuli or visual imitation of an instructor are very inefficient. The student in trying to swing at a tennis ball inadvertently continues to form undesirable habits. The result is a tennis stroke which uses large amounts of energy, is physically tiring to the player, and develops an erratic stroke in which the direction of the tennis ball is hard to control.
It is a principal object of this invention to provide a tennis training device which furnishes the student with a physically detectable and visually apparent indication of incorrect tennis racket swing with respect to the proper amount of grip squeezing strength on the handle.
The degree of tightness with which one squeezes the grip of a racket during the period of acceleration toward the oncoming ball, at the moment of impact, and during the period of the follow-through of any stroke determines to a significant extent the control and power of that stroke.
An advantage of this invention is that the student can both feel and observe immediately the effect of an insufficient amount of force of grip squeeze during the tennis swing.
Yet another advantage of this invention is that the presence of an instructor is often wholly unnecessary in the development of a correct tennis swing.
In playing tennis, the player connot be constantly checking his racket to assure that the position of his hand on the racket handle is proper during each stroke. He must keep a very firm grip on the racket handle to counteract the considerable centrifugal forces of a fast stroke, for example, a serve or to counteract the torque resulting from the ball engaging the opposite end of the racket.
The invention hereof addresses itself to these problems of proper and improper grip during the performance of any stroke motion.
It is quite usual to strike a ball with the racket head at a substantial radial distance from the longitudinal axis of the handle, which will produce a torque tending to rotate the handle within the player's grip. The conventional tennis racket handle is somewhat rounded, which shape when combined with a slippery grip resulting from perspiration will commonly result in relative rotation between the handle and player's hand under the influence of this torque.
In the forehand stroke of tennis, the torque produced by the force of the ball striking the racket head and the moment arm from the striking point to the forefinger of the player's hand tends to rotate the racket about a generally vertically extending axis passing through the gripping forefinger to separate the end of the racket handle from the player's palm portion that is adjacent the little finger. This results in a tendency to weaken the stroke and can be counteracted only by a tight and strong grip upon the handle. Also, a ball hitting the strings or edge of the racket to the side of center will cause the handle of the racket to rotate in the user's hand.
Individual preferences will change the angle of the hand with respect to the longitudinal axis of the handle for a player's own conventional grip. In any event, the purpose hereof is to teach the player the correct degree of pressure. to be exerted by him upon his grip regardless of the type of grip he may conveniently and naturally expound.
The conventional tennis racket handle does not have a fixed reference for circular orientation or for the axial position of the racket relative to the hand, so that the player depends merely on the subjective feeling of the grip for holding the racket always in the same position. In addition, the forehand stroke is considered by many players to be basically unstable. This instability is generated by the limited load carrying capability of the hand in the forehand stroke condition, as partially explained above. The circumference of the cross-section of a conventional racket handle averages about 41/2 inches. With the fingers and the thumb wrapped around the handle, the grip around the outer portion of the hand is strong and stable since the forefinger and thumb together can overlap the whole circumference of the handle; however, the grip is weaker and therefore is unstable at the inner portion of the hand defined by the little finger, because the little finger alone cannot overlap the circumference of the handle. Consequently, the grip can loosen and open a gap between the palm and the handle at the inner region of the hand during a forehand stroke, which concentrates the reaction force of the axial moment on the little finger.